Filter Cloth for Lithium Mining: Spodumene, Lepidolite and Tailings

Recommended material direction

Two variables lead here and they pull in different directions. The feed is a hard-rock silicate — quartz and feldspar gangue — so abrasion is a real failure path rather than a theoretical one. The liquor chemistry, on the other hand, is set by the flotation reagent scheme and may be well away from neutral, and that is the half nobody can infer from the outside.

This narrows the field; it does not pick. Which polymer goes on your machine is settled against your measured numbers and not on a web page — the same position the selection section above takes. What follows is the reasoning behind that position, not a departure from it.

• Polyester (PET) PET

  Continuous reference up to ~150 °C — a published property of the polymer, not a value of ours

  • Acid Good
  • Alkali Limited
  • Hydrolysis Limited
  • Abrasion Excellent

  Excellent abrasion resistance and dimensional stability under tension. If the reagent liquor is neutral or acidic, this is the direction.

• Polypropylene PP

  Continuous reference up to ~90 °C — a published property of the polymer, not a value of ours

  • Acid Excellent
  • Alkali Excellent
  • Hydrolysis Excellent
  • Abrasion Good

  The answer if the reagent scheme runs alkaline and hot, because that is where polyester loses strength from the surface inwards. Abrasion resistance is good rather than excellent, and the reference continuous temperature is the lower of the two.

• Polyamide (Nylon 6 / 6.6) PA

  Continuous reference up to ~110 °C — a published property of the polymer, not a value of ours

  • Acid Poor
  • Alkali Good
  • Hydrolysis Moderate
  • Abrasion Excellent

  Excellent abrasion resistance and good alkali resistance, so it is a candidate where the two leading variables coincide. Acid rules it out, and it changes dimension with absorbed moisture.

What actually decides it The reagent scheme and the measured pH — including the cleaning pH, not only the operating one. A mineralogical breakdown, if the plant has one, settles the abrasion half of the question.

Everything in this block is reasoning from published polymer behaviour applied to the chemistry described further up this page. It is a direction, not a selection — and the selection is made against your measured numbers during the engineering review, then written into the quotation. The full polymer envelope is on the materials page.

Weave options

An abrasive feed and a wide particle distribution push the structure towards strength first and rating second.

• Double layer / multi-layer Two or more interlaced fabric layers woven as one. A fine filtering face carried on a coarse structural back — high strength with fine retention, and drainage channels inside the fabric. Watch: Thicker and heavier; more expensive to weave. The usual answer on heavy belt duties.
• Twill The crossing point steps sideways each pick, giving a diagonal rib. More flexible and more permeable than plain at the same yarn count, with better cake release. Watch: Slightly less dimensionally stable than plain.
• Plain One over, one under. The most stable and the most rigid. Tight, uniform pores; lower permeability for a given yarn. Watch: Least forgiving of dimensional movement; can blind faster on fine solids.

A fine face on a coarse structural back lets the rating and the mechanical life be specified separately instead of trading one against the other in a single layer.

Yarn form. Mono-and-multi combinations are common where the feed carries everything from concentrate fines to gangue grit in the same stream.

Yarn form, weave and surface finish are settled as one decision. The four yarn forms available are monofilament, multifilament, mono + multi combination and staple / spun.

Permeability considerations

Air permeability is the figure everyone compares and the easiest one to quote meaninglessly. It is measured per ISO 9237 at a stated pressure drop — often 200 Pa — or per ASTM D737 (Frazier). A value with no stated pressure and no stated unit is not comparable to anything, including ours. The same applies to a pore or retention rating: on a woven cloth that is a nominal figure and not an absolute cut-off, because woven media do not have a single pore size and the cake quickly becomes the real filter.

Before comparing permeability figures on this duty, settle the machine. A number measured for a belt and a number measured for a pressure filter cloth are not describing the same job, whatever units they share.

How each property is measured, and what to ask any supplier for alongside the number, is set out on the testing and inspection page. Naming the method is a fact about a public standard, not a claim about our laboratory.

Joint options

The descriptions below are written from vacuum belt practice. If your flowsheet turns out to run a pressure filter or a centrifuge instead, the same constructions are judged against different things — which is why the machine is settled first.

• Clipper (metal hook) Interlocking metal hooks crimped onto both cloth ends, joined by a pintle wire. Fitted and replaced on the machine without dismantling it. The fastest change-out. Watch: The joint is a discontinuity: it leaks vacuum as it passes the box, and it is where most belt failures start. Hook material has to suit the liquor.
• PAD / welded overlap The two ends are overlapped and thermally fused. A smoother, quieter joint that seals better than a clipper and carries load more evenly. Watch: Made off the machine or with a portable press; a change-out takes longer.
• Spiral Spiral coils on each end interlaced and pinned. Flexible, drains through the joint, distributes load along the full width. Watch: Adds an open line across the belt — not appropriate where the joint must seal.

Fabricated length, seam squareness and edge treatment are specification decisions rather than shop defaults, and on a wide mining-duty machine they decide belt life as much as the fabric does.

The four constructions drawn in cross-section: how joints fail and what each one costs you.

Edge treatment

• Cut and sealed The cut edge is thermally sealed against fraying. The baseline. Adequate where the machine edge seal is in good condition.
• Folded / hemmed The selvedge is folded back and secured. Adds thickness and stiffness at the edge where the seal rubs.
• Reinforced edge band A separate band is bonded along the selvedge. For machines that chew edges — the usual answer when a belt keeps failing at the edge while its body is sound.
• Coated / sealed band A polymer band is applied to the edge. Seals the edge against vacuum bypass as well as protecting it mechanically.
• Guide strip / tracking profile A profile bonded to the underside to run in the machine guide. Only where the machine is built for it. Fitting one to a machine that is not is a common and expensive mistake.

A reinforced edge band is the usual answer where the belt keeps failing at the edge while its body is still sound. On an abrasive hard-rock duty that failure pattern is the one to watch for.

Relevant equipment

Whatever cloth form this duty turns out to need, it is decided at the loom before it is decided anywhere else: what a weaving platform can hold — pick density, tension, width — sets what the finished cloth can be asked to do. Our weaving runs on DORNIER (Germany) and Sulzer (Switzerland) platforms, machines built for technical textiles rather than for apparel.

Mining-duty cloth is wide and heavy, and holding a consistent pick density across that width is a property of the weaving platform rather than of anything done afterwards. Our own maximum width is being confirmed in writing, so it is answered against your measured dimensions rather than quoted from this page.

Model designations, working widths and installed quantities are being confirmed against the machine nameplates and are not published until they are. A weaving platform is easy to name and hard to fake, and we would rather you were able to check.

The full platform description, the eleven process stations from yarn to crate, and the nine laboratory checks: manufacturing.

Factory capability for this duty

The rows below are the part of our capability envelope that this duty touches. The last group is the one that makes the rest of it worth reading — a supplier who can do everything has told you nothing.

The full envelope, including the machine families and services we decline: what we build to order and what we will not take on. Fifteen pages on how a specification like this is built and read: the filter cloth specification guide.